Vaccine target for devastating livestock disease could change lives of millions

The first ever vaccine target for trypanosomes, a family of parasites that cause devastating disease in animals and humans, has been discovered by scientists at the Wellcome Sanger Institute.

By targeting a protein on the cell surface of the parasite Trypanosoma vivax, researchers were able to confer long-lasting protection against animal African trypanosomiasis (AAT) infection in mice.

The study, is the first successful attempt to induce apparently sterile immunity against a trypanosome parasite. A vaccine was long thought impossible due to the sophisticated ability of the parasites to evade the host immune system. As well as a strong vaccine target for AAT, the findings raise the possibility of identifying vaccine targets for trypanosome species that cause the deadly human infections sleeping sickness and Chagas’ disease.

Animal African trypanosomiasis (AAT) is a disease affecting livestock in Africa and, more recently, South America. It is caused by several species of Trypanosoma parasite, which are transmitted by tsetse flies, causing animals to suffer from fever, weakness, lethargy and anaemia. The resulting weight loss, low fertility and reduced milk yields have a huge economic impact on the people who depend on these animals. The disease has been said to lie at the heart of poverty in Africa.

In humans, a disease called sleeping sickness is caused by infection with another trypanosome species, Trypanosoma brucei. Although control efforts have reduced the number of infections each year considerably, 65 million people remain at risk.

All trypanosome species have developed sophisticated anti-immune mechanisms that allow the parasites to thrive in their host. For example, African trypanosomes display a protein on their surface that constantly changes and prevents host antibodies from recognising the pathogen. Until now, it was thought impossible to vaccinate against trypanosome infection for this reason.

Though drugs exist to prevent or treat AAT, many communities that require them, live in remote locations that are difficult to access. Reliance on a handful of drugs, and a lack of professional expertise in their administration, are thought to be contributing to increased drug resistance in the parasites. An effective vaccine would help to overcome some of these practical barriers.

The next step will be to validate the results using a cattle model. If successful, work could begin on developing a vaccine for AAT that would be an important tool for tackling poverty in affected regions.

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